Two of the most frequent issues encountered when we ship overseas are the time frame and the costs incurred. Some observations and tips from our BH members to ensure smooth passage are:

Be conscious of timeframe, and realize some items (even with International Priority, or Express) may be held up in customs and out of your control.

With custom orders it may be helpful to convo before completing the transaction, or clearly state shop policies regarding fees that may be added on due to shipping costs to various countries.

Realize that a delay in payment may not be an international issue, but maybe more due to the buyer being a newbie, and unsure of how to complete payment. So always say "Thank you for your purchase! Your item is ready to ship out as soon as payment has been completed. If you are having trouble on how to complete payment, you can refer to this tutorial: http://www.etsy.com/help_guide_checkout.php"

Regular first class mail is usually not much more than domestic mail. (Compare that to Priority. One member had a Canadian buyer who requested Priority International -- Canada Priority Mail -- that cost $15 and took 6 weeks to get there).

To send something regular first class mail you need a customs declaration form. Keep in mind that the receiving country may have duties that the seller has to pay. Because of that, one member lists the product value at $50 or under and simply puts "craft items" in the description.

Some countries can be problematic. Consider Fedex or DHL when shipping to any country in Africa, Latin America and Eastern Europe, or countries without reliable home mail delivery.